Solvents from coal tar



July 23, l'942- I J. E. HARVEY, J 2,291,331

SOLVENTS FROM COAL TAR Filed Aug'. 14, 1940 mman/Anm@ Ml/waff Patented July 28, 1942 SOLVENTS FROM COAL TAR Jacquelin E. Harvey, Jr., Atlanta, Ga., assigner of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Appiication August 14, 1940, SeralNo. 352,653

1 Claim.

This invention relates to the production of solvents.

More specifically, the present invention relates to the induction of solvency in tars of aromatic content and fractions thereof, including pitches.

An object of the present invention is the induction of solvency in tars of aromatic content and fractions thereof by the step-wise action of hydrogen.

Further objects of the present invention will become apparent from the following disclosures.

Starting materials of the present invention are tars of aromatic content and fractions thereof derived from coal, wood, petroleum, gas and/or gases. Especially attractive as a starting material is tar derived from coal, as for instance, coke oven tar, gas house tar, or low temperature tar. These tars derived from coal, and more especially coke oven tar, are characterized by the presence of high molecular complexes that are so susceptible to thermal degradation that the solvents of the present invention cannot be provided by a single action of hydrogen, but must be produced in step-wise manner as hereinafter described. By the process of the present f invention it is further possible by recycling operation to substantially convert the entirety of the starting material remaining liquid into the solvents of enhanced value.

The invention will be understood from the following description of illustrative steps comprising various methods of securing the objects of the invention, when read in connection with the accompanying drawing wherein the figure is a diagrammatic sketch of an apparatus for carrying out a form of the process of the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indicated by legend.

Example 1.-A high residue creosote having substantially 48% boiling above 355 C. and substantially 2% coke residue is charged to a high pressure autoclave and subjected to the action of hydrogen at 200 atmospheres pressure and a temperature of 400 C.; catalyst molybdenum oxide; time of reaction, one hour. At the end of the hour period the beneciated creosote is withdrawn from the autoclave and will be found to have reduced coke residue, specific gravity and viscosity. The beneciated material is then dispressure 200 atmospheres; catalyst molybdenum oxide. The thus beneciated material will be found to have an increased solvency as compared to its intermediate starting material, and will be further characterized by having an increment of low boiling fractions in excess of fractional increment in the higher boiling range. The residue incidental to above stripping operation being recycled for further solvent production. The first action of hydrogen is characterized by preferential action on the high boiling range.

Example 2,-A coal tar, specific gravity 1.1641, coke residue in excess of 8% and boiling predominantly above 190 C. is passed through a high pressure reaction vessel while simultaneously flowing hydrogen therewith at a temperature of 410 C. and 350 atmospheres pressure; catalyst tin sulfide; time of reaction, '75 minutes; flow of hydrogen 12,000 cubic feet per barrel feed. The beneciated tar is distilled to an upper limit of 260 C. to provide the distillate as an intermediate starting material. The intermediate starting material is then passed through a high pressure reaction vessel while simultaneously owing hydrogen therewith; catalyst molybdenum sulfide; flow of hydrogen 6,000 cubic feet per barrel of feed stock and time of contact two minutes. The beneficiated material will be found to have a solvency in excess of its intermediate starting material and will be characterized by an increment of low boiling fractions In excess of fractional increment in the high boiling range.

Example 3.-A tar fraction of aromatic content, initial boiling point substantially 220 C. and having substantially a 50% residue above 355 C. is subjected to the action of hydrogen While contacting a cobalt sulfide catalyst; temperature 410 C.; pressure 400 atmospheres; time of contact one hour. The beneciated material will be found to have a lowered coke residue, specific gravity and viscosity, and a condensation of boiling points toward the lower end. The beneciated material is distilled to an upper limit of 320 C. with the distillate serving as intermediate starting material. The intermediate starting material is subjected to the action of hydrogen at a temperature of 465 C. and a pressure of 200 atmospheres. The finally beneciated material will be found to have a solvency in excess of its intermediate starting material and will be further characterized by an increment of low boiling fractions in excess of fractional increment in the higher boiling range.

Example 4.-A coal tar pitch specific gravity 1.23 and boiling at 355 C. is subjected to the action of hydrogen at 375 C. and 200 atmospheres pressure; catalyst molybdenum sulfide; time of contact one hour. The benerlciated pitch is again subjected to an identical cycle of hydrogenation. The twice beneciated pitch is distilled to an upper limit of 210 C. to provide a distillate as an intermediate starting material for the solvents of the present process; the distillate is then subjected to the action of hydrogen at 535 C. and a pressure of 200 atmospheres.

. The beneciated distillate will be found to have a solvency in excess of its intermediate parent material and will be further characterized by an increment of low boiling fractions in excess of fractional increment in the higher boiling range. Y

In the step-wise action of hydrogen in the present invention, the rst action of hydrogen on the starting material is characterized by reduction of coke residue, specific gravity and viscosity in the starting material. In the first cycle or^ hydrogen action pressures as low as 50 atmospheres are usable as are temperaturesV as low as 200 C., however, higher temperatures and pressures are preferred, as for instance, but not as a restriction, temperatures of S50-450 C. and pressures of in excess of 200 atmospheres. Pressures and temperatures are, however, not restricted to any definite limitations inasmuch as hydrogen actions that reduce the coke residue, specific gravity and viscosity of the starting material will proceed at lowered temperatures and pressures. The desired temperatures and pressures are those that will reduce coke residue specific gravity and viscosity in a commercial manner. When using continuous operation in the rst hydrogen cycle flows of 10,000-15,000 cubic feet per barrel feed stock has proven satisfactory, however, higher and lower gas flows have proven effective.

In the last cycle of hydrogen action, as'comprising a part of the present invention, for a given coordination of temperature and pressure as compared to the rst cycle, the hydrogen :dow in the last cycle is less than the iiow in the first cycle. In the last cycle of hydrogen action pressures as low-as 50 atmospheres are usable as are temperatures as low as 250 C. However, more elevated pressures and temperatures are preferred, as for instance, pressures of in excess of 200 atmospheres and temperatures chosen from the range between 30G-'750 C.

Aromatic tars of petroleum derivation or as produced from gas or gases serve as suitable starting materials. 'Iars or fractions thereof, at least once refined by hydrogen or by other means also serve as starting material.

By the term beneciated as used herein and in the appended claims is meant the starting or intermediate starting material at least once subjected to the action of hydrogen in accordance to the present process.

Catalysts assist in speeding and directing the desired reaction of the process of the present invention. All catalysts effective in the presence of hydrogen are usable. Catalysts may be used in various shapes or forms; deposited inwell known manner on carriers; cobalt, tin, vanadium, Vmolybdenum, manganese, chromium, tungsten, or their compounds; promoted or not; in admixture if desired, with or without small amounts of acid, acids, halogen or derivatives of halogen; all sulde and/or oxide catalysts, in the form of shapes, pellets, extruded lengths, comminuted, with or without the presence of other materials possessing hydrogenating properties, or not; such as asbestos, quartz, earths, lumps of brick, etc.

In both cycles of hydrogenation, the present process is predicated on so controlling the reaction conditions that ring structures are not opened with the subsequent formation of liquid chain or paraffin structures to the extent that the solvents of enhanced solvency of the present invention are impossible to manufacture.

In the first cyclic action of hydrogen reaction, conditions are so controlled as to induce no substantial percentage of carbonaceous increment. When utilizing most of the starting materials, the first action of hydrogen is further characterized by the depolymerization of high molecular complexes. By the term high molecular complexes is meant those high boiling fractions especially susceptible to thermal degradation.

The hydrogen supply used in the present process may come from any convenient source, as for instance, by the disassociation of methane. If desired, any diluting gas may be used in connection with the hydrogen.

When the starting material has beensubjected to the first cycle of hydrogen action that reduces coke residue, specific gravity and viscosity, the stripping of the beneficiated mass may be effected at any point desired, as for instance, at 200 C., or higheigor lower. Generally the point of stripping is determined by the boiling range desired in the product flowing from the final action of hydrogen in the second cycle.

The time element in the second cycle of hydrogen action, periods of two minutes have proven satisfactory to provide illustration of the present invention, however, longer or shorter periodsV may be used, as for instance, several minutes. Generally, the time element in the first cycle of hydrogen action is longer than in the second.

Within the limits of the boiling range of the finally beneficiated material, solvents and/ or plasticizers may be fractionated therefrom, as for instance, to provide substitutes for the boiling ranges of any of the following:

Product: Boiling range C. Benzol '78-120 Toluol -150 Hi-flash naphtha -200 High boiling crudes 150-290 Plasticizers -360 The residue incidental to aforesaid stripping action, or any residue incidental to solvent or plasticizer recovery from the finally beneficiated intermediate starting material may be recycled for further product production. By such recy cling operation the coke residue inherent to the starting material can be made to substantially nally disappear.

Starting material includes tars and fractions Y thereof derived from wood, coal and petroleum including gases of carbon content; as for instance, wood tar, pine tar, coke oven tar, gas

When reference is made to high molecular complexes as contained in the starting material, and when the starting material contains 10W boiling fractions that are not considered high molecular complexes, it is of course obvious that the high molecular complexes contained in the starting material are to a certain extent depolymerized by the solvent present.

Starting materials of the present process also include tars of aromatic content from which low boiling fractions have been removed, as for instance, tars from which solvent oils have been removed. Viewed broadly, the starting materials of the present process are tars of aromatic content, fractions of said tar more viscous than the starting material due to removal of low boiling fractions, high boiling fractions and pitches.

The term coal tar as used herein means high temperature coal tar as for instance, high temperature coke oven tar or gas house tar.

Minor changes may be made Within the scope of the appended claim Without departing from the spirit of the invention. In the claim affixed to this specification no selection of any particular modification is intended to the exclusion of other modifications thereof.

I claim:

In the production of solvents from a mixture of high temperature coal tar fractions, the process which comprises: subjecting said material to a relatively high iioW of hydrogen in excess of about 10,000 cubic feet per barrel feed stock at a temperature above 400 C., a pressure in excess of about 200 atmospheres and for such a length of time as to reduce specic gravity and viscosity; stripping low boiling fractions from the beneciated mass and subjecting at least a portion of said 10W boiling fractions to the action of a relatively low flow of hydrogen while contacting a molybdenum compound as catalytic material at a pressure of at least about 50 atmospheres and a temperature selected between the limits of LF75-535 C.; and continuing the operation of the phase last named for such a length of time as to provide a material of induced solvency.

JACQUELIN E. HARVEY, JR. 

